i dunno, people are using rust effectively to build applications too. and apple has started using swift in the kernal.

i do agree that applications are probably best built in fast garbage collected language. but it also seems like go, java, C#, etc have other downsides that push people towards things like zig or rust even for apps. it also depends on what you mean by "apps". is a server an app? what about an actual native cross-platform desktop application? does go, c#, or java have a good paradigm for that? what if you want to use an oss language not tied to a big tech company? you start running out of suitable languages pretty dang fast.

you could name any application type and i could probably give you reasons why you might want to build it in a "systems" language instead of a high level one.